1. Field of the Invention
The present invention relates to an array antenna capable of controlling an antenna characteristic.
2. Description of the Background Art
A conventional array antenna includes a cavity resonator, a feeder element, and a plurality of slot lines. The cavity resonator has a substantially cylindrical shape and is made of metal. The feeder element is provided in the cavity resonator. The plurality of slot lines are arranged substantially in parallel to one another on a cylinder end surface of the cavity resonator in a direction of a rotation axis of the cylindrical shape.
An electromagnetic wave emitted from the feeder element by feeding electric power thereto is emitted outside the cavity resonator through the plurality of slot lines arranged on the cylinder end surface (see “Print Slot Yagi-Uda Antenna with Through-hole Cavity,” Manabu Yamamoto, Naoki Kobayashi, and Kiyohiko Itoh, Communications Society Conference 2001, The Institute of Electronics, Information and Communication Engineers, p 165).
In addition, a radial line slot antenna is known as a conventional array antenna (see “A Basic Study of Radial Line Slot Antenna for 60 GHz Band Wireless LAN,” Akira Akiyama, Tetsuya Yamamoto, Makoto Ando, Naohisa Goto, and Eriko Takeda, Proceedings of the 1997 IEICE General Conference, B-1-85). The radial line slot antenna is a planar array antenna using a radial line as a waveguide. The terminal end portion is short-circuited, and provided with matching slots for canceling reflection. Fed from a central portion, electric power propagates through radial waveguides.
When slot elements are arranged concentrically in the radial line slot antenna, a conical beam is emitted when the element is excited in axially symmetrical manner. Meanwhile, when the element is excited in a rotating electromagnetic field mode, a beam in a front direction can be emitted.
Moreover, an H-type slot antenna including slots has conventionally been known as an antenna that can be mounted on a notebook-type PC (personal computer), a PDA (personal digital assistant) or the like (see “A Study on Double Resonance H-Type Slot Antenna,” Akira Itakura, Yoshinobu Okano and Minoru Abe, The IEICE Transactions on Communications (B), Vol. J86-B, No. 12 (December 2003) pp. 2533–2542). The H-type slot antenna is implemented by a slot formed in an H-shape, and it can be adapted for use in both 2.4 GHz band and 5.2 GHz band. The H-type slot antenna is mounted on a surface of a notebook-type PC. In this manner, the H-type slot antenna can be arranged in the vicinity of metal.
Furthermore, an antenna apparatus including one feeder element and six parasitic elements has conventionally been known as an antenna allowing electrical switching of directivity (see Japanese Patent Laying-Open No. 2002-261532).
In this antenna, the feeder element has one end fixed to a dielectric support substrate and arranged substantially perpendicular to the dielectric support substrate. Six parasitic elements are divided into three groups of two parasitic elements, and respective groups are provided on three printed boards. Three printed boards are arranged substantially perpendicular to the dielectric support substrate.
Here, three printed boards are arranged on the dielectric support substrate such that six parasitic elements are arranged around the feeder element located in the center and on a perimeter of a circle having a prescribed radius.
As described above, a variety of antennas have conventionally been known.